Conventionally, there have been proposed and sold various types of analyte testing/observing apparatuses used for testing whether cells move in a certain direction without assistance, observing a state in which cells move in a certain direction without assistance, measuring the number of cells having moved in a certain direction without assistance, separating cells which move in a certain direction without assistance, or a like purpose. The present applicant also proposed an analyte testing/observing apparatus of such a type in WO/2005/028611 (Patent Document 1) or the like. This devised apparatus is excellent in operability, easy to operate, and enables highly accurate testing and observation of cells.
Incidentally, in such an apparatus, the following procedure is performed to cause cells (analyte) and a reagent to react with each other and test and observe the behavior of the cells. A microplate having a plurality of wells which accommodates the cells, and a microplate having a plurality of wells which accommodates the reagent are prepared. Appropriate amounts of the cells and the reagent are dispensed from the wells of the respective microplates to reaction wells within a chamber of a cell observation apparatus, and the cells and the reagent are caused to react within the reaction wells, whereby the behavior of cells is tested and observed.
Of microplates each having a plurality of wells for storing cells or a reagent, some microplates include 1500 wells each. When the cells or the reagent is dispensed from the large number of wells of such a microplate to, for example, 48-channel reaction wells, the cells or the reagent accommodated in the wells of such a microplate easily evaporates at room temperature. Therefore, it is necessary to suppress evaporation of moisture from the cells or the reagent, to thereby prevent drying of the cells or the reagent. Further, in the case where the reaction wells are formed by a large number of depressions of another microplate, it also becomes necessary to suppress evaporation of moisture from a mixture of the cells and the reagent dispensed into the reaction wells, to thereby prevent drying of the mixture.
In an analyte test apparatus disclosed in Japanese Patent Application Laid-Open (kokai) No. 2002-40031 (Patent Document 2), a plate cover having a predetermined number of openings is provided to cover, from the upper side, an area through which a microplate having a plurality of reaction wells each storing a mixture of a dispensed analyte and a dispensed reagent is transferred by a transfer apparatus. Only when the reactions within the reaction wells are tested and/or observed or the reaction wells are cleaned, the openings are opened. Thus, evaporation of moisture from the mixtures is suppressed, whereby drying of the mixtures is prevented. This structure enables obtainment of stable test results in an analyte test.
However, the plate cover of the analyte test apparatus disclosed in Patent Document 2 is fixed, and the microplate is moved. In addition, since a clearance is always preset between the microplate and the plate cover, the analyte test apparatus has a problem in that moisture easily evaporates from the mixture of the analyte and the reagent accommodated in each reaction well of the microplate, so that drying of the mixture progresses quickly. Moreover, since a lid for opening and closing the openings of the plate cover is formed of a flat plate member, a horizontally extending large space is needed so as to move the plate member to thereby open the opening portions. Therefore, the conventional analyte test apparatus cannot meet the requirement of space saving for an analyte testing/observing apparatus of such a type, which is used in a narrow space such as a laboratory.
Further, the conventional microplate mounting stand does not have means for preventing evaporation of moisture from (i.e., preventing drying of) cells or a reagent accommodated in wells of a microplate mounted on the mounting stand before being dispensed.
Patent Document 1: WO/2005/028611
Patent Document 2: Japanese Patent Application Laid-Open (kokai) No. 2002-40031